Heavy-duty, off-road vehicles such as a HD-1200M by Komatsu or a Volvo BM A25 are typically used to transport earthen loads in work areas such as open pit mines and the like. Such work areas vary in condition, depending primarily upon the geographic features of the land, the local climate and day-to-day changes in weather. Although heavy-duty, off-road vehicles are designed to operate over a wide variety of terrain and under all types of climatic conditions, it is not unknown for the vehicles to lose traction and require assistance. To free a vehicle, a chain or cable can be rigged to the vehicle for pulling it from the area causing the problem. Although this approach may ultimately prove successful in freeing the vehicle, it is a time-consuming and sometimes dangerous operation. In part because of the foregoing reasons, rigging a chain to the vehicle is often not done; instead, a bulldozer or similar type vehicle is used to push the stuck vehicle from behind. This necessarily results in the bulldozer pushing on the body since the frame is not accessible from the back.
The dump bodies of heavy-duty, off-road vehicles are not designed to accept the application of horizontal forces from the rear of the body which naturally results from pushing on the body. Besides damage to the bed of the body, the pivot assemblies joining the body to the frame experience forces which are generally transverse to the direction of the force they are designed to withstand. Such transverse forces can cause significant damage to the pivot assemblies.
Pushing on the rear of the dump body could be avoided if the frame of the vehicle extended to the same posterior area as occupied by the end of the body. In this connection, bumper-type extensions of the frame have traditionally been viewed as unpractical since it is necessary that the area under the dump body and to the rear of the pivot for the body be clear so as to allow rotation of the body during dumping of a load. If rear bumper-type extensions are impractical, front bumpers are of little value since it is highly unlikely for two vehicles to collide head-on. Operation of off-road, heavy-duty vehicles without bumpers, however, does represent a significant danger. Specifically, the relatively high elevation of the dump body and the overhang of the posterior portion of the body past the frame can damage the cab of a vehicle which collides with the back of another vehicle. Moreover, the end of the body can be at the level of the operator and possibly cause serious physical injury.